We study the binding of the coenzyme pyridoxal 5'-phosphate to a variety of enzymes by a variety of techniques. We use fluorescence spectroscopy, uv spectroscopy, nmr spectroscopy, binding of coenzyme analogs, and kinetics of coenzyme binding as measures of enzyme-coenzyme interactions. Second, we study the mechanisms of pyridoxal 5'-phosphate dependent enzymes. We have studied extensively an abortive pathway of amino acid decarboxylation which may be of importance in a variety of disease states. We also use various kinetic methods to study mechansims of enzyme action. Third, we use chemical modification of proteins to identify functional groups at the active sites of enzymes. BIBLIOGRAPHIC REFERENCES: M.H. O'Leary and R.L. Baughn, "New Pathway for Metabolism of Dopa", Nature, 253, 52 (1975). H.F. Gilbert and M.H. O'Leary, "Arginine as a Substrate Binding Site in Aspartate Aminotransferase", Biochem. Biophys. Res. Commun., in press.